A known cellular communication network employs so called network assisted D2D communication between user equipments (UEs). Thanks to the D2D communication a load on the cellular communication network may be reduced. The load can be measured in terms of for example radio resource usage, traffic between a base station and a user equipment. In particular, load on the radio base station, comprised in the cellular communication network, may be reduced.
With the network assisted D2D communication, user equipments are allowed to use licensed spectrum resources to communicate directly with one another via a so called D2D link. In contrast, with cellular communication methods, data is transmitted through an access point, such as the radio base station, between the two user equipments. The D2D link connects the two user equipments directly, without passing user data via the radio base station. Hence, the radio base station is off loaded.
Before the D2D link may be established, the two user equipments need to detect that they are located in the proximity of each other. The detection of nearby user equipments is referred to as D2D discovery, because the user equipments discover, or detect, each other. For the purpose of discovery, special beacon signals are sent by the user equipments. The beacon signals are typically sent on a subset of radio resources allocated to the cellular radio communication network.
WO2011/063845 discloses a method for performing beacon broadcasting in a D2D network. A cellular communication network comprises a base station and a node and a further node. The node and the further node may be terminal devices. The D2D network comprises the node and the further node. A D2D communication link may be established between the node and the further node. A set of channels dedicated for the purposes of beaconing may be set by the base station. The node, capable of entering the D2D communication network, selects a channel for broadcasting from a set of channels dedicated for informing node properties in the D2D communication network. The selection is based on the characteristics of the node and/or the state of the node. Then, the node causes a broadcast of information related to at least part of the properties of the node on the selected channel. This way, the information is not only within the signal transmitted on the beacon channel but also with position or index of the employed beacon channel.
Disadvantageously, the node and the further node may select the same beacon channel when the characteristics and state of the node and the further node match. Thus, beacons, from the node and the further node, sent on the selected beacon channel collide. As a result, degenerated beacon transmission occurs.